So I've replaced both upper and lower control arms with UPR's chrome-moly arms with urethane bushings; the rear differential housing does have the urethane bushings as well but those are getting changed out for replacement OEM style rubber bushings in the next week or two. I'm hoping that helps this issue.

This is a street driven car, no track time, and generally driven pretty easy on the streets.

I can hear what I believe to be the axles turning in the rear end, and it's not quiet. It's a noise that is speed dependant. It's not really a grinding, or a whine, but more of a rubbing sound. Axle bearings and seals are brand new and axles have nearly no pitting or scaring. Fluid is brand new with Motorcraft friction modifier.

Is it normal with urethane control arm bushings to hear an increase in rear end noise in the cabin? Is this just part of having a solid axle RWD car that's 23 years old? Is there anything I can do, or at least anything to reduce the amount of noise transmitted into the cabin?

I have MM EXTREME Duty on my of convertible with Teflon bearing on owned end and three piece urethane in the other. Stock replacement Ford rubber bushing on the upper arm. The noise is barely more audible than the stock arms. On my previous Fox I had BBK with solid urethane that made way more noise. I think what you are hearing is all the noise from the bushings binding. I believe solid urethane bushings on a fox mustang are a bad idea especially on the upper arm.

I also have MM XD lowers and when first installed they transmitted a lot of gear noise and I was really worried about how loud it was. But after a few couple hundred miles they broke in and no more noise. The best suspension mod I made by far.

I have MM EXTREME Duty on my of convertible with Teflon bearing on owned end and three piece urethane in the other. Stock replacement Ford rubber bushing on the upper arm. The noise is barely more audible than the stock arms. On my previous Fox I had BBK with solid urethane that made way more noise. I think what you are hearing is all the noise from the bushings binding. I believe solid urethane bushings on a fox mustang are a bad idea especially on the upper arm.

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You are correct the best and most efective is an spherical Heim joint but they are noisy and not ideal for a street car , I run Heims up top but car is no longer a daily

Totally normal. I have mm maximum duty lowers with solid bushings with the little thin urethane pucks and the axle noise is terrible

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Let me tell you...what a relief hearing this.

Again, I'm planning to replace the differential housing bushings with the OEM rubber bushings and get rid of the poly bushings currently in there. I'll still have poly bushings in the upper arms where they connects to the frame, but I'm not sure I'm willing to change the upper arms out to a spherical joint or back to the stock upper arm.

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It's a bit off topic, but you guys running non-rubber bushings in the upper arm mounts, the ones on top of the 8.8", do they help with wheel hop?
Our Fox body Fairmont has tremendous wheel hop since it does not have quads.
All of our suspension bushings throughout the car are poly, except the stock rubber bushings on top of the rear end.
It has the tubular upper and lower control arms, non-adjustable, GT Mustang rear sway bar, new stock replacement coil springs w/poly isos, and Moser girdle on the rear. 4.10 gears and stock TL unit...
Any ideas on stopping wheel hop?

THANK YOU for the noise info! This is why I (careful how I say this) want harder durometer rubber bushings. I do not want axle whine or squeak. How about adding grease zerks to your arm ends if there are none?

What grease and where from? It used to be they specked a Silicone product only for poly bushings.

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In my Foxes, I use spherical upper housing bushings to eliminate bind.

Poly control arm bushings do transmit a little more sound than the OEM rubber bushings, but not much.

My initial reaction to the OP's noise description is that it sounds like a ring & pinion backlash problem which may have been masked by the OEM control arms. But that's just arm chair quarterbacking over the internet. I'd recommend to have someone experienced with Fox suspension ride in the car to offer their opinion.

Boostfrk- I just noticed you're in Florida. I'm in Fort Myers and UPR is in West Palm. Are you close to either of us so we could check it out for you?

Sharad - Thanks for the offer man, I really appreciate it. I'm in north/esat central FL. West Palm is about 3 hours south of me and Ft. Myers is closer to 4 or 5.

I recently switched rear ends (complete rear end swap) and the rear end I swapped in had the poly bushings in the upper housing above the pumpkin. So, I went to a rear end that I don't know the exact condition of and poly bushings in the differential housings; hard to say which one is the culprit since I introduced 2 variables at once. It could be either. I figure since it's easier and cheaper to replace the differential housing bushings, and a good idea anyways, I'll start there and see what happens. If the noise is still present I'll dig deeper and start to suspect some issue with the rear end.

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Sharad - Thanks for the offer man, I really appreciate it. I'm in north/esat central FL. West Palm is about 3 hours south of me and Ft. Myers is closer to 4 or 5.

I recently switched rear ends (complete rear end swap) and the rear end I swapped in had the poly bushings in the upper housing above the pumpkin. So, I went to a rear end that I don't know the exact condition of and poly bushings in the differential housings; hard to say which one is the culprit since I introduced 2 variables at once. It could be either. I figure since it's easier and cheaper to replace the differential housing bushings, and a good idea anyways, I'll start there and see what happens. If the noise is still present I'll dig deeper and start to suspect some issue with the rear end.

So I've replaced both upper and lower control arms with UPR's chrome-moly arms with urethane bushings; the rear differential housing does have the urethane bushings as well but those are getting changed out for replacement OEM style rubber bushings in the next week or two. I'm hoping that helps this issue.

This is a street driven car, no track time, and generally driven pretty easy on the streets.

I can hear what I believe to be the axles turning in the rear end, and it's not quiet. It's a noise that is speed dependant. It's not really a grinding, or a whine, but more of a rubbing sound. Axle bearings and seals are brand new and axles have nearly no pitting or scaring. Fluid is brand new with Motorcraft friction modifier.

Is it normal with urethane control arm bushings to hear an increase in rear end noise in the cabin? Is this just part of having a solid axle RWD car that's 23 years old? Is there anything I can do, or at least anything to reduce the amount of noise transmitted into the cabin?

I hate noises like this...

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Boostfrk,

did you finally figure out what the problem was with this noise? I'm pooling data and considering to Urethane/Poly or NOT. I'm street driven too - no track.

You can read some many opinions on this stuff til you get dizzy from all the yes yes yes , no no no's!

It's a bit off topic, but you guys running non-rubber bushings in the upper arm mounts, the ones on top of the 8.8", do they help with wheel hop?
Our Fox body Fairmont has tremendous wheel hop since it does not have quads.
All of our suspension bushings throughout the car are poly, except the stock rubber bushings on top of the rear end.
It has the tubular upper and lower control arms, non-adjustable, GT Mustang rear sway bar, new stock replacement coil springs w/poly isos, and Moser girdle on the rear. 4.10 gears and stock TL unit...
Any ideas on stopping wheel hop?

Click to expand...

I just swapped to adjustable uppers a few months back and had the mechanic set my pinion angle while he was going over my 4.10 swap. After he threw in some negative angle, I started have horrible wheel hop. Not so much from a dead start, but more from a roll then punching it (I'm on 555R's). I stiffened up my rear Strange shocks (like an 8 setting) and it helped tremendously. However, last night I was coming home around 3:00am and we have had a cold snap (about 40 degrees). I punched it from a roll and about knocked my fillings out from all the axle hop. I think the cold tires and pavement just make it worse. I will eventually put a fresh set of quad shocks back on. Unforetunately, I think this is the only permenant solution, except perhaps a completely redesigned rear suspension. Oh yeah, I have all poly pieces, even the 8.8 housing.

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I just swapped to adjustable uppers a few months back and had the mechanic set my pinion angle while he was going over my 4.10 swap. After he threw in some negative angle, I started have horrible wheel hop. Not so much from a dead start, but more from a roll then punching it (I'm on 555R's). I stiffened up my rear Strange shocks (like an 8 setting) and it helped tremendously. However, last night I was coming home around 3:00am and we have had a cold snap (about 40 degrees). I punched it from a roll and about knocked my fillings out from all the axle hop. I think the cold tires and pavement just make it worse. I will eventually put a fresh set of quad shocks back on. Unforetunately, I think this is the only permenant solution, except perhaps a completely redesigned rear suspension. Oh yeah, I have all poly pieces, even the 8.8 housing.

Joe

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I figured that the quads might be the solution...
We have all the stuff to do it, but his frame rails are not drilled for mounting the hardware, and we'll have to drop the gas tank to set up the quads properly.

I don't blame my son for not wanting to drop his tank again... we have done it many times.
He said this morning his car is acting like the fuel pump is failing, so we might have an excuse to do it before long.